1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device using, for example, a stencil mask as a transfer mask and an apparatus for manufacturing the semiconductor device.
2. Description of the Related Art
There has been known a method in which in semiconductor device manufacturing process, a stencil mask having a predetermined pattern is set above a substrate to be processed at a predetermined distance and charged particles such as electrons or ions are projected onto the substrate through openings defining the pattern of the stencil mask. In the method, charged particles (ion beam) such as ions accelerated from a particle source by a predetermined energy pass through a scanner and a magnet to be formulated into a patterned ion beam. The patterned ion beam is projected onto the substrate through the openings formed in the stencil mask. The substrate to be processed mentioned here is a semiconductor substrate, on the surface of which a semiconductor device is to be formed or has been formed, not shown.
There is a disadvantage that, when a substrate is processed using the charged particles, residue charges are accumulated on the substrate so that the semiconductor device formed on the substrate may be destroyed by being charged due to the accumulated charges. A conventional method is known to overcome this disadvantage (Jpn. Pat. Appln. KOKAI Publication No. 9-283411, see page 4). In this method, secondary electrons or plasma electrons are generated to neutralize the accumulated charges, thus preventing the destruction of a substrate due to the accumulated charges.
Jpn. Pat. Appln. KOKAI Publication No. 2002-203806 (FIGS. 29 and 35) discloses a method of controlling the amount of charges accumulated on a substrate to be processed. In the method, a distance and a potential difference between a stencil mask and the substrate to control the amount of charges accumulated on the substrate. The controlling of the amount of charges is carried out by providing a power supply between the stencil mask and the substrate, or by providing a power supply between the stencil mask and the ground and also another power supply between the substrate and ground.
However, neutralizing the accumulated charges by generating secondary electrons or plasma electrons is sensitive to the amount of charges on the substrate and the stencil mask, the amount of energy on charged particles, degree of vacuum in the apparatus, etc., and the amount of neutralized charges greatly changes depending on these factors. As a result, with the method of neutralizing the accumulated charges by generating secondary electrons or plasma electrons, the neutralized charge amount may be insufficient or an excessive amount of electrons may be supplied to cause negative charging, which possibly destroy the semiconductor devices. Further, the charge neutralizing mechanism, which generates the secondary electrons or plasma electrons, is complicated in structure.
On the other hand, according to the method of controlling the amount of the charges accumulated on the substrate by changing a distance and a potential difference between the stencil mask and the substrate, yield is improved. However, it is necessary to set up the distance and the potential difference between the stencil and the substrate before an ion implantation process is carried out. There is no problem if the irradiation condition of the charged particles is stable and the state of the apparatus is stable during the processing. However, if the apparatus is unstable, and the irradiation amount (current amount) of the charged particles per unit time changes during the processing, the neutralized charge amount may be insufficient, or an excessive amount of electrons may be supplied to cause negative charging, which leas to a possible destruction of the semiconductor devices.